Catalyst composition, its preparation and use

ABSTRACT

An unsupported catalyst composition which comprises one or more Group VIb metals, one or more Group VIII metals, and a refractory oxide material which comprises 50 wt % or more titania, on oxide basis, which is prepared by precipitation techniques, finds use in the hydroprocessing of hydrocarbonaceous feedstocks.

This application is a division of application Ser. No. 10/783,130, filedFeb. 20, 2004, now U.S. Pat. No. 7,557,062.

FIELD OF THE INVENTION

The present invention concerns catalyst compositions having a highmetals content, their preparation and use in hydroprocessing,particularly hydrodesulphurisation and hydrodenitrogenation.

BACKGROUND OF THE INVENTION

Hydroprocessing reactions involve the application of hydrogen to asubstrate, usually under elevated temperature and pressure, in thepresence of a catalyst with the aim of causing a physical or chemicalchange in the substrate. Most such hydroprocessing reactions occur inrefinery operations where the substrate is a hydrocarbon feedstock.

Conventional hydroprocessing catalysts are generally in the form of acarrier of a refractory oxide material on which hydrogenation metals aredeposited, the choice and amount of each component being determined bythe end use. Refractory oxide materials usual in the art are amorphousor crystalline forms of alumina, silica and combinations thereof. Theseoxide materials can have some intrinsic catalytic activity but oftenonly provide the support on which active metals compounds are held. Themetals are generally base or noble metals from Group VIII and Group VIBof the Periodic Table which are deposited in oxidic form duringmanufacture; in the case of base metals, the oxides are then sulphidedprior to use to enhance their activity.

The use of titania, or titanium dioxide, as a catalyst support for aconventional hydroprocessing catalyst is limited by the lack of a usefulpore structure. Therefore the few titania-supported commercialhydroprocessing catalysts that exist in the market have a low porevolume and as a result can hold or support less hydrogenation metalsthan the more common alumina-supported catalysts. Generally it is viewedthat thermal stability, low surface area and poor mechanical strengthhave all hindered the commercial exploitation of titania supportedcatalyst systems. The intrinsic activity of hydrogenationmetals-on-titania is, however, superior to eg alumina-based catalysts.The proposals available in the art attempt to harness this intrinsicactivity and remedy the deficiencies of low metals loadings and thermalinstability by using mixed oxides.

M. Breysse et al in Catalysis Today 86 (2003) 5-16, notes that themolybdenum loading on a typical titania supported system is generallylimited to 6 wt % Mo because of the low surface area of the support butwith recent improvements in preparing mesoporous titania this can beexpected to increase to 10 to 12 wt %. Tests using a typicalhydrogenation metal combination of nickel and molybdenum showed that aNiMo-titania catalyst had the lowest activity for tetralin conversion inthe presence of H₂S than NiMo on various mixed titania-alumina supports,and NiMo-alumina catalysts. Later in the same review article it isconcluded that the presence of nickel or cobalt suppresses the higherintrinsic activity of molybdenum-titania systems.

G. M. Dhar et al. in Catalysis Today 86 (2003), 45-60, also looks atvarious mixed alumina-titania supported systems; hydrogenation metalsare applied by the conventional incipient wetness impregnation methodand an improved HDS and hydrogenation activity is attributed toincreased metals dispersion. Here the presence of small amounts (3 wt %)of nickel and cobalt are considered to promote, eg, HDS activity of acatalyst of 8 wt % molybdenum on mixed titania-alumina supports. In astudy of variation of Mo loading, the maximum molybdenum contentconsidered is 14 wt % (as the oxide and basis total catalyst).

Also proposed in the art for hydrotreating and particularly for use inhydrodesulfurization (HDS), especially deep desulfurisation of dieselfractions, are catalyst compositions which contain refractory oxidematerial but which are made via co-precipitation. European Patentspecification EP-A-1090682 describes one such co-precipitation proposalto prepare a hydrotreating catalyst, which catalyst has variousproperties including a crystalline phase, such as alpha-alumina, viewedas necessary for high activity and to impart mechanical strength andtherefore a longer service life in commercial use.

By co-precipitation, the incorporation of a dispersed metals contentinto a conventional carrier material is attempted by enabling intimatecontact between metals compounds and carrier material and thus enablingthe metals to become dispersed through the carrier material beforeshaping. This contrasts with conventional impregnation techniques whereonly a small amount of metals deposition is possible since the shapedcarrier is already formed and there are diffusional and spacelimitations for the metal ions or compounds to become dispersed throughthe catalyst support.

Alternative catalyst forms have been proposed for use in thehydroprocessing of, for example, refinery streams. One such group ofcatalysts are termed ‘bulk catalysts’. Such catalysts are formed frommetal compounds only, usually by co-precipitation techniques, and haveno need for a catalyst carrier or support; see for example WO 00/42119,U.S. Pat. No. 6,162,350 and WO 00/41810. These publications disclosebulk Group VIII and Group VIb metal catalysts and their preparation anduse. U.S. Pat. No. 6,162,350 discloses that such catalysts may containone or more of each metal type, and examples show NiMo, NiW and the mostpreferred NiMoW bulk catalysts. The preference in U.S. Pat. No.6,162,350, WO 00/42119 and WO 00/41810 is that no binder is incorporatedinto the final catalyst composition since the activity of the bulkcatalyst composition may be reduced (U.S. Pat. No. 6,162,350, Column 14,lines 10 to 114). If, however, a binder is to be used the resultingcatalyst composition comprises the bulk catalyst particles embedded inthe binder with the morphology of the bulk catalyst particlesessentially maintained in the resulting catalyst composition (U.S. Pat.No. 6,162,35, Col. 14, lines 24 to 30). The binder when present ispreferably added prior to shaping but can be added at any stage in thecatalyst preparation.

The use of titania as a refractory oxide material or binder is proposedas one of many suitable oxide materials in these patent publications,but there is no indication that its use is actually contemplated orexpected to provide any benefit over the alumina- and silica-bound formsexemplified.

In refinery processes, feedstocks contain a variety of contaminants, themain ones being sulfur and nitrogen. While sulfur reduction has alwaysbeen desirable, increasingly strict regulations on gas emissions eg frommotor vehicles, is driving the need for catalysts which can provideultra low sulfur fuels. For effective HDS activity, and especially forthe deep desulfurisation required for environmental reasons, a catalystmust be effective to remove all sulfur compounds, whether simple orcomplex. Nitrogen contaminants, while often low in amount, can have asevere poisoning effect on catalysts and also adversely affect endproduct storage stability and quality. The poisoning effect on catalystsis such that a catalyst effective for, eg HDS, of a pure chemicalfeedstock may be ineffective or short-lived when exposed to an impurerefinery feedstock.

Thus, there is a continuing demand for hydroprocessing catalysts forfeedstocks having both sulfur and nitrogen contaminants, which catalystshave a significant hydrodesulphurisation activity for both simple andcomplex sulfur-containing compounds in the presence of nitrogencontaminants but even more desirably also have a high or improvedhydrodenitrogenation (HDN) activity.

SUMMARY OF THE INVENTION

It has now surprisingly been found that when titania is incorporatedinto an unsupported or precipitated catalyst in significant amounts, theresulting catalyst composition has a substantially higher HDS and HDNactivity than the use of alumina or silica alone. This is achieved withthe use of nickel and cobalt as hydrogenation metals and not justmolybdenum (and/or tungsten) alone. High metals contents can besustained in the catalyst compositions of the invention; they can beprocessed and used in high temperature environments, and a comparablemechanical strength to conventional commercial supported hydroprocessingcatalysts is found.

Accordingly the present invention provides an unsupported catalystcomposition which comprises one or more Group VIb metals, one or moreGroup VIII metals, and a refractory oxide material which comprises 50 wt% or more titania, on oxide basis.

Also provided is a process for the preparation for the catalystcomposition of the invention, and its use in hydroprocessing.

DETAILED DESCRIPTION OF THE INVENTION

This invention relates to the hydroprocessing of chemical and petroleumfeedstocks using a catalyst composition containing Group VIII(especially Ni and/or Co) and Group VIB (especially Mo and/or W) metalsand an inert refractory oxide, of which 50 wt % or more is titania.

Herein reference is made to the Periodic Table of Elements which appearson the inside cover of the CRC Handbook of Chemistry and Physics (‘TheRubber Handbook’), 66^(th) edition and using the CAS version notation.

The term ‘hydroprocessing’ is used herein to cover a range ofhydrotreatment processes where the hydrocarbon feed is brought incontact with hydrogen in order to modify key physical and chemicalproperties.

The catalyst composition of the present invention is an unsupportedcatalyst composition comprising at least one Group VIII metal, at leastone Group VIb metal and a refractory oxide material of which at least 50wt % is titania.

By the term ‘unsupported’ it is to be understood that the composition isnot of the conventional form which has a preformed, shaped catalystsupport which is then loaded with metals via impregnation or deposition,but is a composition in which the metals and refractory oxide materialare combined together when the composition is formed prior to anyshaping step. Generally this combination will occur throughprecipitation. Unlike supported catalysts, in this unsupported catalystcomposition, the refractory oxide material is no longer a separatedistinct material within the composition. However, the presence oftitanium can in most cases be identified from an XRD powder diffractionanalysis, and it is also possible to determine the components of thecomposition and the proportion of the composition that is derived fromthe titania-containing refractory oxide material by analyticaltechniques common in the art, such as XRF (X-Ray Fluoresence) and ICP(Inductively-Coupled Plasma Spectrometry Analysis).

The titania is present as 50 wt % or more of the refractory oxidematerial. Preferably it is present in an amount in the range of from 70to 100 wt %, especially in the range of from 90 to 100 wt %. It isespecially present in an amount in the range of from 95 to 100 wt %. Itis especially preferred that titania is the predominant and particularlythe sole component of the refractory oxide material. If other refractoryoxide material is used, then suitably this is selected from alumina,silica, magnesia, zirconia, boria and zinc oxide. Good results have beenfound using a mixture of titania and silica as refractory oxidematerial.

Titania is naturally available in several forms or polymorphs: rutile,anatase and brookite. The most thermally stable form of titania isrutile and at very high temperatures the anatase form can transform intothe rutile form. Any of these forms of titania may be present in thecatalyst composition of the invention. Good results have been achievedusing titania having in excess of 70 wt % in the anatase form, mostsuitably 80 to 100 wt %, and especially 100 wt % anatase.

It has been found that the particle size of the titania can influenceand accentuate the activity of the final catalyst composition. While alltitania powders are suitable for use in the present invention, it ispreferred that titania powder having an average particle diameter of 50microns or less is used, preferably a particle diameter of 20 microns orless and especially a particle diameter of 5 microns or less. Generallythe minimum average particle diameter of particle in the titaniautilised is of the order of 0.005 micron. Herein average particlediameter is the diameter of 50% of the particles, also termed D_(v)50.

Very suitable titania starting materials are available from MilleniumChemicals, Degussa and Haishunde. For example Millenium's DT-51D and G5grades; Degussa's P25 grade and Haishunde's grade FCT010925. Mixtures oftitania and other refractory oxide materials are also readily availablecommercially, for example silica-titania mixtures such as grade FTS 01from Haishunde.

The B.E.T. surface area of the titania utilised is suitably in the rangeof from 10 to 700 m²/g, more preferably from 20 to 400 m²/g.

The Group VIII metal is preferably one or two non-noble metals selectedfrom nickel, cobalt and iron. Preferably the Group VIII metal isselected from nickel, cobalt and a combination of nickel and cobalt.Most preferably the Group VIII metal is nickel. The Group VIb metal ispreferably one or two non-noble metals selected from chromium,molybdenum and tungsten. The Group VIb metal is more preferably selectedfrom molybdenum, tungsten and a combination of the two. The mostpreferred Group VIb metal is dependent on the temperature of end use. Inapplications where the end use is in a reactor temperature of below 380°C., it is preferably molybdenum, and where the end use temperature is380° C. or above, it is preferably tungsten or a mixture of molybdenumand tungsten.

A preferred catalyst composition of the present invention, expressed inelemental form, is a catalyst composition of the general formula, on anoxide basis,(X)_(b)(M)_(c)(Z)_(d)(O)_(e)  (I)wherein

-   X represents at least one non-noble Group VIII metal;-   M represents at least one non-noble Group VIb metal;-   Z represents titanium and optionally one or more elements selected    from aluminium, silicon, magnesium, zirconium, boron and zinc;-   O represents oxygen;    one of b and c is the integer 1;    and    d, e, and the other of b and c each are suitably a number greater    than 0 such that the molar ratio of b:c is in the range of from    0.2:1 to 10:1, the molar ratio of d:c is in the range of from 0.1:1    to 30:1, and the molar ratio of e:c is in the range of from 3.4:1 to    73:1;

As above X is preferably one or two non-noble metals selected fromnickel, cobalt and iron. Preferably X is selected from nickel, cobaltand a combination of nickel and cobalt. Most preferably X representsnickel. The metal M is preferably one or two non-noble metals selectedfrom chromium, molybdenum and tungsten. M is more preferably selectedfrom molybdenum, tungsten and a combination of the two. The mostpreferred metal M is dependent on the temperature of end use, as above.

The element represented by Z together with a portion of the oxygencomponent is derived from the refractory inorganic oxide startingmaterial. Most preferably Z represents titanium as the predominant,especially the sole, element. As optional additional elements Z,aluminium and silica are the most preferred. Additional small amounts(in the range of from 1 to 3 wt %) of zinc oxide in the refractory oxidestarting material can be advantageous to increase surface area of thecatalyst composition.

The numbers b, c, and d represent the relative molar ratio values whichare given taking one component as a standard or reference. Herein one ofb and c is taken as the reference and designated as the integer 1. Theother values are then established as relative values, basis one of themetals X and M on an oxide basis. The number e indicates the molar ratiovalue for oxygen in the composition (I) which will be set by thestoichiometry of (X)_(b)(M)_(c)(Z)_(d)(O)_(e).

Preferably c is the integer 1, and the ratio b:c is in the range of from0.4:1 to 7:1, most preferably 0.5:1 to 5:1, especially 0.8:1 to 3:1; theratio d:c is in the range 0.2:1 to 10:1, most preferably 0.3:1 to 5:1,especially 0.4:1 to 3:1; and this results in ratio e:c being in therange of from 3.8:1 to 30:1, most preferably 4.1:1 to 18:1, especially4.6:1 to 12:1.

Good results have been obtained when X is nickel; M is molybdenum; Z istitanium; O is oxygen; c is 1; b:c is in the range of from 0.5:1 to 3:1,especially 0.8:1 to 2.5:1, and is most especially 1:1 to 2:1; d:c is inthe range of from 0.2:1 to 4:1, especially 0.3:1 to 3:1, and is mostespecially 0.4:1 to 2:1; and e:c is in the range of from 3.9:1 to 14:1,especially 4.4:1 to 12:1, and is most especially 5:1 to 9:1.

Depending on the method of preparation that is followed to prepare thecatalyst composition for use in the invention, there could be residualammonia, organic species and/or water species present; followingdifferent methods, different amounts as well as different types ofspecies can be present. In respect of water, also atmospheric conditionscan affect the amount present in the catalyst composition. Therefore toensure that the catalyst composition definition is not distorted byatmospheric or preparation conditions, the definition used herein, onboth an elemental basis and on percentage amount basis, is given on anoxide basis.

To establish the catalyst composition on an oxide basis, an elementalanalysis is performed on a sample once all volatiles have been removed,eg by thorough heating for example at a temperature in excess of 400° C.for a minimum of 60 minutes, in accordance with standard practice in theart.

Expressed on a percentage weight basis, very suitably the amount ofGroup VIII metal(s) lies in the range of from 2 to 80 wt % as the oxideand based on total catalyst, but preferably is in the range of from 6 to75, more preferably 10 to 65, especially 14 to 53 wt %. Very suitablythe amount of Group VIb metal(s) is in the range of from 5 to 90 wt % asthe oxide, preferably 10 to 80 wt %, more preferably 15 to 75 wt %, andespecially 27 to 70 wt %.

The total amount of Group VIII and Group VIb metals in the compositionof the invention, as the oxide, is very suitably in the range of from 30to 95 wt %, preferably 50 to 95 wt %. The minimum amount of total metalsis suitably 30 wt %, but is generally 50 wt %, more preferably 65 wt %,and especially 70 wt %. Preferably the maximum amount is 95 wt %, morepreferably 90, especially 85 wt %. The total amounts of metals isespecially substantially 80 wt %.

The balance of the catalyst composition, on an oxide basis, is generallyderived from a refractory oxide material, suitably in an amount in therange of from 5, more preferably from 10, and especially from 12 wt %,to 70 wt %, preferably to 50, more preferably to 35, most preferably to30, especially to 25. Preferred compositions contain from 10 to 30 wt %,more preferably from 15 to 25 wt %, and especially contain substantially20 wt %, on an oxide basis.

Good results have been obtained when X is nickel and is present in anamount in the range of from 8 to 55 wt %, preferably 13 to 50 wt %, andespecially 17 to 44 wt %; when M is molybdenum present in an amount inthe range of from 20 to 80 wt %, preferably 30 to 70 wt %, andespecially 35 to 66 wt %; and when titanium is present in an amount inthe range of from 8 to 40 wt %, preferably 10 to 35 wt %, and especially15 to 30 wt %, all on oxide basis, i.e. in the form of NiO/MoO₃/TiO₂

In a catalyst composition for use in the invention, when not assessed onan oxide basis, there may be in the range of from 0 to 10 wt %, basistotal catalyst, of residual species, eg organics, ammonia and/or waterspecies, and most commonly from 3 to 8 wt %. The presence and amount ofsuch components can be determined by standard analysis techniques.

The catalyst composition of the present invention may be prepared by anysuitable precipitation process. The present invention therefore furtherprovides a process for the preparation of a catalyst composition of thepresent invention, wherein one or more Group VIb metal compounds arecombined with one or more Group VIII metal compounds, and with atitania-containing refractory oxide material, in the presence of aprotic liquid and optionally an alkali compound; and the catalystcomposition is recovered following precipitation.

The preparation process may very suitably be by the procedure describedin U.S. Pat. No. 6,162,350, in WO 00/41810, or indeed described inEP-A-1 090 682, in which the metal compounds are either fully dissolvedor partly dissolved in the liquid used, suitably protic liquid,especially water or water-containing liquid, with the addition of theappropriate amount of refractory oxide material to one of the startingcomponents or to a mixture of starting components. Where fully dissolvedmetals and alkali compound are both utilized, it is preferred that asolution of fully dissolved metals is added to a slurry of refractoryoxide material and alkali compound; this gives preferred materials overthe process of addition of alkali compound to a slurry of solidrefractory oxide and fully dissolved metals.

Most preferably, however, the preparation is by a process whichcomprises heating a precursor composition which is in the form of, or isrecovered from, a slurry, optionally after aging at a temperature in therange of from 20 to 95 deg C. for a minimum of 10 minutes, said slurrybeing obtained by (co)precipitating, at a sufficient time andtemperature, one or more Group VIb compounds, one or more Group VIIIcompounds, one or more refractory oxide materials, and an alkalicompound, in a protic liquid. This process yields material which giveshigh crush strength when shaped eg extruded. Where the metal compoundsare used as solids (and one or more partly dissolve when coming intocontact with the protic liquid), the crush strength of the resultingshaped catalyst is even higher, though the reason for this is not fullyunderstood.

Thus preferably, the metal compounds utilised in the process of theinvention are added to the protic liquid in solid form.

The metal compounds and refractory oxide are suitably utilised in thepercentage weight amounts already discussed above.

Expressed in elemental terms, the preferred catalyst composition ispreferably prepared by decomposition of a precursor of the generalformula(NH₄)_(a)(X)_(b)(M)_(c)(Z)_(d)(O)_(e)  (II)in which a is a number greater than 0, and X, M, Z, b, c, d and e havethe meanings given above. The molar ratio of a:(b+c) is suitably from0.1:1 to 5:1, preferably from 0.1:1 to 3:1, especially 0.5:1 to 2:1.Preferably c is the integer 1 and the molar ratio b:c is from 0.4:1 to7:1, more preferably from 0.5:1 to 5:1, especially 0.8:1 to 3:1; themolar ratio represented by d:c is preferably from 0.2:1 to 10:1, morepreferably from 0.3:1 to 5:1, especially 0.4:1 to 3:1; and the molarratio represented by e:c is preferably from 3.8:1 to 30:1, morepreferably 4:1 to 18:1, especially 4.6:1 to 12:1.

The decomposition or heating of the precursor is performed at anelevated temperature in the range of from 100 to 600° C., preferablyfrom 120 to 450° C., more preferably at a temperature in the range offrom 250 to 400° C. The decomposition may take place in an inertatmosphere, such as under nitrogen, any noble gas or a mixture thereof,or in an oxidative atmosphere, e.g. in oxygen, oxygen-nitrogen, air, ora mixture of one or more thereof, or in a reductive atmosphere, such ashydrogen, hydrogen sulfide, or a mixture thereof. The decomposition maytake place during processing of the slurry or during further processingof the composition for use, eg during extrusion or calcination before orafter shaping.

The preferred preparation process of the present invention involvescontacting one or more slurries of the desired metals in a protic liquid(for example water) wherein one or more of the metal compounds,especially both, are in solid and dissolved phase simultaneously, with arefractory oxide in the presence of an alkali compound at a temperatureand for a time sufficient to produce the precursor. It is possible foreach metal type that the metal is provided by two metal compounds, oneof which is soluble in the protic liquid and the other of which is onlypartly soluble. Metal in this context does not refer to the metals inmetallic phase but to metallic compounds containing the necessary metalions.

It is possible for all components to be added to the protic liquid atthe same time or sequentially. Also it is possible for one or more ofthe metal compounds and the refractory oxide to be in slurry phase withthe protic liquid, and for the remaining components to be added thereto.

The process of the invention most suitably involves the mixing of slurryphase mixtures of the Group VIb and Group VIII metal(s) compounds inwater or other protic liquid blended at elevated temperature with aslurry of an alkali compound and the refractory oxide material also inwater or other protic liquid. While the order of addition to formslurries from the individual compounds is not critical for the formationof the catalyst composition of the invention, we have found that whenthe alkali compound is added to a slurry of partly dissolved metals andthe refractory oxide, very useful catalytic materials are given. It is,however, possible to add the metals' slurry to the alkali compound, withthe refractory oxide present in one or the other or both, and stillobtain useful catalytic compositions.

Blending or mixing can be carried out by any conventional means, eg ananchor stirrer, or high energy, high impact method, for example using anUltra Turrax machine.

During the mixing or blending process, the components of the slurries(co)precipitate to form solids of the precursor composition preferablyunder the action of the alkali precipitation agent. Normally the term‘co-precipitation’ is used when two or more compounds that aredissolved, precipitate out of solution together. In the preferredprocess of the invention, a portion of the compounds are not dissolvedand it is possible that one or more dissolved components precipitateonto the solid component(s). Therefore we prefer to use herein theterminology ‘(co)precipitation’ when referring to precipitation ofmaterials at least one of which is in a partly dissolved state. Theprocess of the invention is suitably controlled through the maintenanceof an appropriate temperature for an appropriate time to achieve thedesired precursor. It is a routine matter to determine the appropriatetemperature/time combinations for a desired end product. Suitably thetemperature will lie in the range of from 25 to 95° C. and the(co)precipitation time will lie in the range of from 10 minutes to 2hours. While essentially desired end products will arise from a controlof both conditions, it is noted that operating the (co)precipitationprocess at higher temperatures may cause too much dissolution of themetals components to enable a good end-product; at too low a temperaturethen insufficient dissolution may occur.

In a preferred embodiment, an initial slurry concentration of in therange of from 2 to 40, preferably 2 to 25 wt % of nominal solids contentis aimed for. By nominal solids content, the amount of solids added tothe protic liquid is intended. Preferably the amount of alkali compound,eg ammonia, in the slurry is at least 0.2 mol per mol of metals M+X, onan oxide basis, and at most 50 mol per mol of metals M+X, on an oxidebasis. The quantity of alkaline material can affect the final form ofthe catalyst composition. The amount of alkaline material, eg ammonia,preferably applied should be at least 0.75 mol, more preferably at least0.8, especially at least 0.9 mol, per mol metals M+X, oxide basis. Theamount of alkali compound utilized is preferably at most 5, morepreferably at most 3, and especially at most 2, mol per mol metals M+X,oxide basis.

Suitable Group VIII compounds, which stay in partly solid phase if thesolvent is water, and therefore are preferred, are nickel carbonate,nickel oxide, nickel hydroxide, nickel phosphate, nickel formiate,nickel sulfide, nickel molybdate, or a mixture of two or more thereof.Additionally soluble salts such as nickel nitrate, sulphate or acetatemay be used in combination with one or more of these compounds and/orwith each other. The corresponding cobalt or other Group VIII metalcompounds are also suitable. Suitable, and preferred, molybdenumcompounds (based on a similar criteria) are molybdenum (di or tri)oxide, ammonium molybdate, molybdic acid, molybdenum sulfide, ormixtures thereof. These materials are commercially available or can beprepared by commonly known laboratory practices, e.g. by precipitation.The corresponding tungsten or other Group VIb metal compounds are alsosuitable.

Starting materials having a C, H, and O component in addition to thedesired metals are, in general, more preferred due to a lesser impact onthe environment. Nickel carbonate is therefore more preferred, since itcan decompose to nickel oxide, carbon dioxide and water upon heating,based on the carbonate content of the starting material.

Suitable alkali compounds applied to prepare the slurry with therefractory oxide material are selected from hydroxides or oxohydroxides,for example, Group IA, or IB or Group IIA, or IIb hydroxides, Group IAor Group IIA silicates, Group IA, or IB or Group IIA or IIB carbonates,and equivalent ammonium compounds, or mixtures of any two or morethereof. Suitable examples include ammonium hydroxide, sodium hydroxide,ammonium silicate, ammonium carbonate, and sodium carbonate. Preferablythe alkali compound is one that will generate ammonium ions in solution;this includes ammonia which, with water as the solvent, will generatethe ammonium hydroxide form.

It is generally preferred to utilise mixing and precipitationconditions, which keep the solvents below the boiling point temperaturesof the applied solvent, i.e. below 100° C. in case of water. The pH ofthe slurries is generally kept at their natural pH during the entirepreparation process. However additional adjustment of the pH can beconveniently achieved, if desired, by using suitable acidic or alkalinecompounds generally known in the art.

The formed slurry is optionally held at ambient or elevated temperaturefor a period of time (commonly termed ageing) subsequent to the end ofthe (co)precipitation process. The ageing time usually lies in the rangeof from 10 minutes, suitably 30 minutes, to preferably 4 hours; theageing temperature may be in the range of from ambient temperature, forexample, from 20, suitably from 25° C., to 95° C., preferably from 55 to90, and especially from 60 to 80° C. The ageing period is optionallyfollowed by cooling the obtained mixture to a lower temperature.

After optional cooling, the obtained slurry may be processed in a numberof different ways in order to regain the solid content, which processcan involve filtration, spray drying, flash drying, evaporation, andvacuum distillation. By evaporation, any process of driving off theprotic liquid, e.g. water, or drying is intended, for exampledessication and boil down processes. The system used will depend on anumber of local factors including environmental legislations, and energyavailability. Most preferred are filtration and spray drying. The formeris quick and not energy intensive but requires several reiterativesteps, especially in closed loop manufacturing processes where themother liquor is reused, and produces higher volumes of waste water; thelatter is energy intensive but generates little waste.

The most preferred combination is to use the preferred slurrypreparation process (utilising alkali compound) in combination withspray drying.

The so-prepared solid product is a powder which has a loss on ignitionLOI of 5 to 95%.

Herein loss on ignition (LOI) for a material is the relative amount oflost mass upon heating the material to 540° C. following the procedure:The sample is mixed well to prevent any inhomogeneity. The weighedsample is transferred into a weighed and precalcined crucible. Thecrucible is place to a preheated oven at 540° C. for a minimum time of15 minutes, but typically for 1 hour. The crucible containing the driedsample is weighed again, and the LOI is determined according to theformula:LOI%=(w−w _(calc))/w*100%where w is the original weight of the sample, w_(calc) is the weight ofthe calcined sample after heating in the oven, both corrected with theweight of the crucible.

The prepared powder may be dried before optional further processing,especially where filtration has been used to isolate or recover thesolids. This drying or ageing can take place in any suitable atmosphere,e.g. inert, such as nitrogen, noble gases, or mixtures thereof, oroxidative gases, such as oxygen, oxygen-nitrogen mixture, air, ormixtures thereof, or a reductive atmosphere, such as hydrogen, ormixtures of reductive and inert gases or mixtures thereof, with orwithout ammonia and/or water moisture present. The drying temperature ispreferred to lie in the range of from 20, usually 25, to 200° C.,preferably 55 to 150° C. and especially from 70 to 130° C.

The powder may be used as such or, more preferably is used as a shapedcatalyst formulation.

Optionally the obtained powder is calcined prior to shaping. Suitablecalcination temperatures are in the range of from 100 to 600° C.,preferably from 120 to 450° C. eg under 400° C. The calcination may alsobe carried out in any suitable atmosphere, e.g. inert gases as nitrogen,noble gases or a mixture thereof, or in a reactive atmosphere, e.g.oxygen, oxygen-nitrogen, air, or a mixture of one or more thereof, or amixture of inert and reactive gases.

Prior to shaping, the obtained powder is optionally mixed withadditional materials in either solid or liquid phase. Those in solidstate include catalytically active materials, e.g. other catalyticmaterials generally used in hydrotreating applications. It is alsopossible to combine the obtained powder with catalytically activematerials that are used in other hydroconversion processes, for examplehydrocracking. Thus the powder may be combined with a crackingcomponent, such as a zeolitic or other component that promoteshydrocracking—the conversion of a hydrocarbon feedstock to one of alower boiling point. Such components include faujasite materials, suchas zeolite Y, ZSM-5, ZSM-21, zeolite beta, or combinations thereof.Certain amorphous silica alumina materials have a cracking function andmay be utilised. It is unnecessary to add to the powder any materialthat would act solely as a binder, but of course it is possible.

Where desired, other supplementary materials can be added. These includematerials usually added during conventional catalyst preparations.Suitable examples are phosphorus materials, e.g. phosphoric acid,ammonium phosphate, or organic phosphor compounds, boron compounds,fluor containing compounds, rare earth metals, additional transitionmetals, or mixtures thereof. Phosphorous compounds may be added at anystep of the preparation. If e.g. alumina is used as part of therefractory oxide material, phosphorous compounds can be used forpeptising (with or without nitric acid).

Moreover, added materials may include additives typically referred inthe art as ‘shaping agents’ or ‘shaping aids’. Those additives maycomprise stearates, surfactants, graphite, or mixtures thereof. Formaximum strength in the resulting shaped materials however, particularlywhere shaping is by extrusion, then it is preferred to minimize theamount of any conventional extrusion aids. Most preferably, shaping isperformed by extrusion in the absence of any extrusion aids.

The dried powders prepared by decomposition of the precursor compound,can exhibit crystalline reflections when examined by powder XRDdiffraction analysis. These reflections are characteristic of thetitanium (and any cobalt) in the prepared material. Following shaping byextrusion and calcination it has been found that some of the shapedcatalyst compositions exhibit other reflections which are characteristicof layered double hydroxide material. This material is normallyundesirable in a catalyst material prior to shaping because theresulting extruded product has a reduced crush strength. In thecompositions of the present invention such hydroxide material onlyappears to arise after extrusion in certain cases, and no such reducedcrush strength has been found.

Suitable materials in liquid phase may additionally be added to theshaping mixture obtained, which include protic, e.g. water, polyols,etc., and non-protic liquids, e.g. hydrocarbons. Protic liquids, e.g.water, may be added for example in order to bring the LOI content of themixture to a suitable level for shaping.

In general, there is no particular order of mixing the materials (insolid and/or liquid form) together. What is important is to ensure thatthe sample is mixed well to prevent nonhomogenity. The amount ofadditional solids and liquids added during shaping lies preferentiallyin the range of from 0 to 95 wt % based on final weight, and depends onthe requirements of the anticipated catalytic application. Shaping canbe performed in various ways depending on the requirements of theapplication. Those methods include spray drying, extrusion, beadingand/or pelletizing among others.

Sulfidation may be performed in order to turn one or more metals intoits active form. If the composition is used as a shaped catalystcomposition, then it may be sulfided before and/or after shaping. Nospecial sulphiding procedure is necessary for the catalyst compositionof the invention. In general, sulfidation may be carried out bycontacting the catalyst or precursor with a sulfur containing material,e.g. elemental sulfur, sulfides, disulfides, etc. in gas or liquidphase. Sulfidation can be carried out at any step of the shapingprocedure, including prior to the first optional drying step. It ispreferred, however, that sulfidation is carried out only prior toshaping when any of the subsequent heat treatments performed are carriedout under a suitable atmosphere that prevents the conversion of the(partly) sulfided phase back to an oxide state.

Preferably the sulfidation step is carried out subsequent to the shapingstep(s), and, if applied, subsequent to the last calcination step. Thesulfidation may be carried out ex situ (with an appropriate procedure)prior to loading the catalyst into a hydroprocessing unit. Commonex-situ procedures are the ACTICAT process (CRI International Inc.) andthe SULFICAT process (Eurecat US Inc.). It is however preferred that thelast sulfidation procedure is carried out in situ as follows.

The catalyst is sulfided into the active catalyst form by means ofsulfidation carried out in the presence of hydrogen, by eithercontacting the catalyst with liquid feedstock (in liquid or partlygaseous phase), which contains and/or is enriched in sulfur, wheresulfur is present in the form of an organic sulfur compound and/orelemental sulfur, or in the presence of a sulfur containing gas, or amixture thereof.

Surface area of the final shaped product measured by the B.E.T. method,using nitrogen as adsorbate, generally lies in the range of from 10 to350 m²/g, preferably from 30 m²/g, more preferably from 40 m²/g topreferably 300 m²/g, more preferably 200 m²/g. Pore volume of the finalproduct, measured using nitrogen adsorption up to 95 nm on the B.E.T.adsorption curve, preferably lies in the range of from 0.002 to 2.0cm³/g, preferably from 0.05 to 1.5 cm³/g, more preferably to 1.2 cm³/g.Most preferred is a pore volume in the range of from 0.08 to 1.0 cm³/g.Flat bed crush strength, as measured by ATSM D 6175, is preferably inexcess of 100 N/cm.

Catalysts which comprise a catalyst composition of the present inventionexhibit a very high activity for hydrodesulphurisation andhydrodenitrification of hydrocarbon feedstocks. This activity is higherthan that found for equivalent NiMo and CoMo catalysts prepared by(co)precipitation with alumina or silica.

While not wishing to be bound to any theory, it is currently thoughtthat this exceptional activity is the result of a high dispersion factorfor the metals through the oxide material, achieved through the carefulcontrol of the (co)precipitation process. High dispersion should not beconfused with uniformity of dispersion; the catalyst compositions foruse in and of the invention have a high activity with metals dispersedthrough the oxide material, but are not necessarily uniformly dispersed.

The catalyst compositions of the invention have a particularly goodactivity for hydrodesulfurisation (HDS) and hydrodenitrogenation (HDN).In the art of refinery processing, a number of terms may be used torefer to processes which require HDS and HDN activity in some form.These terms include hydrotreating, hydrofinishing, hydrofining andhydrorefining. The compositions of the present invention therefore finduse in all these hydroprocessing reactions. Useful hydrogenationactivity particularly of aromatics (also known in the art ashydrodearomatisation) has also been found for these compositions.

Hydrocarbon feedstocks that contain sulfur and nitrogen include anycrude or petroleum oil or fraction thereof which have a measureablesulfur and nitrogen content. The feedstocks may be previously untreatedor have already undergone such treatment as fractionation, for exampleatmospheric or vacuum distillation, cracking for example catalyticcracking, thermal cracking, or hydrocracking, or any otherhydroprocessing treatment.

Examples of suitable hydrocarbon feedstocks include catalyticallycracked light and heavy gas oils, hydrotreated gas oil, light flashdistillate, light cycle oil, vacuum gas oil, light gas oil, straight rungas oil, coker gas oil, synthetic gas oil, and mixtures of any two ormore thereof. Other possible feedstocks include deasphalted oils, waxesobtained from a Fischer-Tropsch synthesis process, long and shortresidues, and syncrudes, optionally originating from tar sand, shaleoils, residue upgrading processes and biomass.

The feedstock may have a nitrogen content of up to 10,000 ppmw (partsper million by weight), for example up to 2,000 ppmw, and a sulfurcontent of up to 6 wt %. Typically, nitrogen contents are in the rangeof from 5 to 5,000 ppmw, most suitably in the range of from 5 to 1500 orto 1000, eg from 5 to 500, ppmw, and sulfur contents are in the range offrom 0.01 to 5 wt %. The nitrogen and sulfur compounds are usually inthe form of simple and complex organic nitrogen and sulfur compounds.

The catalyst compositions may be applied in any reactor type but aremost suited for use in a fixed bed reactor. If necessary two or morereactors containing the catalyst may be used in series.

The catalyst compositions may be applied in single bed and stacked bedconfigurations, where the compositions are loaded together with layersof other treatment catalyst into one or a series of reactors inconsecutive order. Such other catalyst may be for example a furtherhydroprocessing catalyst or a hydrocracking catalyst. Where thecomposition of the invention is exposed first to the feedstock, then asecond catalyst is most suitably a catalyst which is susceptible tonitrogen-poisoning.

The process of use of the invention may be run with the hydrogen gasflow being either co-current or counter-current to the feedstock flow.

The process of use of the invention is operated under the conditions ofelevated temperature and pressure which are conventional for therelevant hydroprocessing reaction intended. Generally, suitable reactiontemperatures lie in the range of from 200 to 500° C., preferably from200 to 450° C., and especially from 300 to 400° C. Suitable totalreactor pressures lie in the range of from 1.0 to 20 MPa.

Typical hydrogen partial pressures (at the reactor outlet) are in therange of from 1.0 to 20 MPa (10 to 200 bar), and preferably from 3.0 to15.0 MPa (50 to 150 bar), especially at 3 to 10 Mpa (30 to 100 bar) atwhich pressure compositions of the present invention have been found tohave a particularly improved activity.

The hydrogen gas flow rate in the reactor is most suitably in the rangeof from 10 to 2,000 Nl/kg liquid feed, for example 100 to 1000 Nl/kg,more suitably 150 to 500 Nl/kg.

A typical liquid hourly space velocity is in the range of from 0.05 to10 kg feedstock per litre catalyst per hour (kg/l/h), suitably from 0.1to 10, preferably to 5, more preferably from 0.5 to 5, kg/l/h.

The compositions for use in the present invention are normally sulfidedbefore use. Such procedures are well known to the skilled person.Suitable procedures have been discussed above.

The following Examples illustrate the present invention.

EXAMPLES

In these Examples the following test methods have been followed toprovide the measurements given B.E.T. Measurement: ASTM D 3663-99, asmodified by ISO 9277, with drying of the sample at 300° C. for 60minutes prior to measurement, and using nitrogen as adsorbate. Porevolume: obtained from nitrogen adsorption up to 95 nm on the B.E.T.adsorption curve.

Nominal composition proportions are given herein as percentages byweight.

With the exception of Examples 9 and 10, the titania used in each of theExamples of the invention is grade DT-51D obtainable from MilleniumChemicals which has a BET surface area of 88 m²/g and is 100% anatasetitania, on oxide basis.

Example 1 CoO/MoO₃/TiO₂ 41 wt %/39 wt %/20 wt %

In a 5 litre bulb, 2933 g water were heated to 80° C. Subsequently 84.2g titania, 273.1 g cobalt carbonate, and 184.9 g ammonium dimolybdate(containing 56.5 wt % Mo) were added to the water. Shortly after, 161.5g ammonia solution (25 wt % ammonia content) were added whilemaintaining the temperature at 80° C. The pH was 9.5. After 30 minutesthe heating was switched off.

The slurry was spray dried. In total 453 g solid material was recovered.The powder was extruded, dried and calcined at 300° C. in air.

The so-obtained extrudates exhibit a B.E.T. surface area of 63.8 m²/g.The nitrogen pore volume, measured up to 95 nm on the B.E.T. adsorptioncurve, was 0.23 cm³/g.

Example 2 CoO/MoO₃/TiO₂ 27 wt %/53 wt %/20 wt %

Into a 2 l bulb, 1506 g water were weighed and heated to 80° C.Subsequently, one after the other, the following compounds were added:42.1 g TiO₂, 95.4 g cobalt carbonate, and 124.1 g ammonium dimolybdate.The slurry was stirred for 5 minutes while the temperature wasmaintained at 80° C. Thereafter, 55.7 g ammonia 25 wt % solution wereadded to the slurry.

The temperature was kept at 80° C. for 30 minutes. The pH was 9.7 (asdetermined from a small test portion cooled to room temperature and thepH measured at room temperature). After 30 min, the heating was switchedoff, and the slurry was spray-dried over about 30 minutes.

The obtained powder was extruded, dried and calcined. The productexhibited a B.E.T. surface area of 56.4 m²/g. The nitrogen pore volume,measured up to 95 nm on the B.E.T. adsorption curve, was 0.097 cm³/g.

Example 3 CoO/MoO₃/SiO₂ Comparative Sample 27 wt %/53 wt./20 wt %

Into a 2 litre bulb, 1000 g water were measured. 124.1 g ammoniumdimolybdate and 91.54 g cobalt carbonate (59.84 wt % CoO) were added tothe water, while stirring with a pseudo-anchor type stirrer. The slurrywas heated to 80° C. over half an hour. Additionally, another slurry of44.9 g silica, (SIPERNAT 50) 502 g water and 55.7 g ammonia (25 wt %ammonia content) was prepared simultaneously.

As soon as the first slurry was at 80° C., it was added to themetal-containing slurry. The temperature was maintained at 80° C. forthe remaining hour, while the pH was 7.4. The resulting slurry wasspray-dried and yielded 206 g of powder.

The powder was extruded, dried and calcined at 300° C. The so-obtainedextrudates exhibited a B.E.T. surface area of 74 m²/g. The nitrogen porevolume, measured up to 95 nm on the B.E.T. adsorption curve, was 0.24cm³/g.

Example 4 Comparison of Gas Oil Test of the Catalysts of Example 1,Example 2 and Example 3

Gas oil hydrodesulphurisation (HDS) testing was performed in a nanoflowsetup under trickle flow conditions, using full range (“virgin”)straight run gas oil as feed. The catalysts were crushed and sieved intoa 30-80 mesh size fraction which is the size most suited for catalytictesting in a tubular trickle flow reactor. After drying, they wereloaded into the reactors with SiC as diluent to ensure proper plug flowconditions. Prior to testing, the catalysts had been sulfided with thefeed itself, according to a procedure generally applied in the refineryfor calcined hydrotreating catalysts.

Testing was performed at 345° C., under 55 bar hydrogen partialpressure, with a hydrogen gas rate of 250 Nl/kg feed. No additional H₂Swas added to the recycle gas. The liquid hourly space velocity (LHSV)was set to 1.75 l.l⁻¹.h⁻¹. The feed contained 1.63 wt % organic sulfur,and 165 ppmw organic nitrogen.

Data for both HDS and HDN (hydrodenitrogenation) performance werecollected. Relative volumetric activities (RVAs) of the catalysts aredisplayed in Table 1, and are based on the pseudo first order reactionrate constants (k) for the two reactions calculated from the sulfur andnitrogen content of the effluent stream. By this, the result of one testrun (here that for the catalyst of Example 3) is set at 100% conversionand the RVA for the other test catalysts indicates what percentageincrease in activity was found. For the catalysts of Examples 1 and 2the HDS RVA values are exceptionally high; the HDN RVA values are alsosignificantly increased.

TABLE 1 Pseudo first order reaction rate constants and relativevolumetric activities of Example 1, Example 2 and Example 3 in HDS andHDN reaction using full range straight run (“virgin”) gas oil as feed.Example 1 Example 2 Example 3 Refractory oxide titania titania silica Sin product (ppmw) 59 64 507 Conversion of sulfur (%) 99.6 99.6 96.9k_(HDS) (l · l⁻¹ · h⁻¹ · % wt S⁻¹) 42.6 41.2 12.8 Relative volumetricHDS 333% 322% 100% activity (%) N in product (ppmw) <1.0 <1.0 4.4Conversion of nitrogen (%) 99.4 99.4 97.3 k_(HDN) (l · l⁻¹ · h⁻¹ · % wN⁻¹) 70.8 70.3 39.3 Relative volumetric HDN 180% 178% 100% activity (%)

Table 1 clearly demonstrates the advantage of using titania as therefractory oxide when formulating the catalyst with CoMo active phase.An order of magnitude lower sulfur content in the product can beachieved by using the titania containing catalyst and the conversion ofboth sulfur and nitrogen is increased significantly reaching almosttotal conversion. When expressed as relative volumetric activity: thehydrodesulfurization activity is approximately three times higher withtitania as refractory oxide present, and hydrodenitrification activityis almost twice as high compared to the silica counterpart.

Example 5 NiO/MoO₃/TiO₂ 27 wt %/53 wt %/20 wt %

In a 5 litre bulb 2972 g water were heated to 80° C. Upon reaching thistemperature, 84.2 g titanium dioxide, 220.3 g nickel carbonate (39 wt %nickel), and 248.5 g ammonium dimolybdate were added to the water.Shortly thereafter, 111.6 g ammonia solution (with 25 wt % ammoniacontent) were mixed with the above slurry. The resulting mixture waskept at 80° C. for 30 minutes. The pH was 8.3.

After 30 minutes the heating was switched off. 344 g of solid materialwere recovered by means of spray-drying. The powder was extruded, andthe obtained green extrudates were dried and then calcined at 300° C.

The B.E.T. surface area of the resulting product was 42 m²/g. The total(nitrogen) pore volume measured up to 95 nm on the B.E.T. adsorptioncurve was 0.123 cm³/g. The elemental analysis gave NiO/MoO₃/TiO₂—27.5 wt%/51.3 wt %/20.8 wt %, which corresponds to b:c=1.0:1, d:c=0.7:1,e:c=5.5:1.

Example 6 NiO/MoO₃/SiO₂ Comparative Sample 27 wt %/53 wt./20 wt %

In a 2 litre bulb 1485 g water were weighed and heated to 80° C.Subsequently 44.9 g Sipernat 50 silica, 108.7 g nickel carbonate (39.5wt % Ni) and 124.3 g ammonium dimolybdate were added, while maintainingthe temperature at 80° C. Shortly thereafter, 55.7 g ammonia solution(25 wt % ammonia content) were added to the slurry.

After 30 minutes, the heating was switched off. The pH was 7.44. Theslurry was spray-dried yielding 204 g of powder in total. The powder wasturned into the final product by extrusion, drying and calcination at300° C.

The B.E.T. surface area of the calcined product was 42 m²/g. Measured upto 95 nm on the nitrogen adsorption curve in the B.E.T. method, thenitrogen pore volume was 0.132 cm³/g.

Example 7 Comparison of Gas Oil HDS and HDN Test of the Catalysts ofExample 5 and Example 6

Following a typical sulfidation procedure resembling an industrial scaleoperation, the catalysts obtained by the procedure of Example 5 andExample 6 were turned into their sulfidic state. The catalytic activityof the so-obtained products was measured in HDS and HDN operation. Thetest data was collected from a microflow tubular reactor under trickleflow conditions using full range straight run (“virgin”) gas oil. Twofeedstocks with close to identical properties were employed; details aregiven in Table 2.

TABLE 2 Selected properties of feeds used in performance testing FeedFeed A Feed B S XRF (wt %) 1.62 1.63 N (ppmw) 152 165 Density (20/4)(cm³/g) 0.86 0.86 TBP at 10% wt (° C.) 241 236 TBP at 50% wt (° C.) 316321 TBP at 90% wt (° C.) 382 388 TBP at 96% wt (° C.) 397 403

Testing was performed under constant effluent sulfur content at 55 barand at 1.0 h⁻¹ liquid hourly space velocity of feed. Test data collectedafter 500 hours on stream, and expressed as the temperature (measured in° C.) required for obtaining 10 ppmw sulfur in the product are shown inTable 3. The obtained nitrogen content in the product at thetemperatures shown is also given in Table 3 as the measure of the HDNactivity.

TABLE 3 Comparison of HDS and HDN activity of catalysts at constanteffluent sulfur content using a full range straight run (“virgin”) gasoil as feed Catalyst Example 5 Example 6 Refractory oxide titania SilicaFeed applied Feed A Feed B Temperature required for 10 ppmw 330 342sulfur in product (° C.) Pseudo first order reaction rate 38.81 25.76constant for HDS (l · l⁻¹ · h⁻¹ · wt % S⁻¹) Relative volumetric activityfor HDS 151% 100% N content in product at reaction <1 <1 temperatures(ppmw) Pseudo first order reaction rate 54.48 41.10 constant for HDN (l· l⁻¹ · h⁻¹ · wt % N⁻¹) Relative volumetric activity for HDN 133% 100%

It can be seen from Table 3 that the catalyst made by using titania asthe refractory oxide, achieves identical sulfur content in the effluent(product) stream at 12° C. lower temperature. When comparing the pseudofirst order reaction rate constants for the HDS reaction, asignificantly higher reaction rate constant is found in the case of thetitania-containing catalyst, compared to the silica counterpart. Thistranslates into a 51% improvement for volumetric activity using thesilica-based catalyst as base case.

The elimination of nitrogen containing molecules from the feed is alsoconsiderably improved by the use of titania as the catalyst support. Asis shown in Table 3, at temperatures where 10 ppmw sulfur was obtainedin the product stream, both catalysts achieved nitrogen contents belowthe detection limit of measurement.

Converting this result into pseudo first order reaction rate constantsfor HDN helps to assess the differences in activity. Based on thereaction rate constants, a 32.6% increase in relative volumetricactivity for nitrogen removal can be attributed to the use of titania(Example 5).

Example 8 Comparison of Aromatic Saturation Activity of the Catalysts ofExample 5 and Example 6

The extent of aromatic saturation under the reaction conditionsdiscussed in Example 7 was also evaluated. In order to eliminatepossible variation in thermodynamic equilibria, the temperature was setto 345° C. in these tests. This ensured comparable sulfur slips for bothcatalysts. Full range straight run gas oil was used as feed, where onlyslight variations in the aromatic content were recorded between the twofeeds applied in the tests.

The conversion levels calculated from aromatics content of the feed andthe product measured in mmol/g (UV method) is listed in Table 4. Twoconditions were measured at 60 bar hydrogen partial pressure, at 200Nl/kg hydrogen gas flow rate applying hourly space velocities of 1.5 and1.0 l.l⁻¹.h⁻¹ at 345° C. As guidance, the obtained sulfur in product(ppmw) is also indicated in Table 4.

TABLE 4 Selected properties of the feedstock used for testing aromaticsaturation performance LHSV (l · l⁻¹ · h⁻¹) 1.5 1.0 UV aromaticsconversion silica titania silica titania Mono aromatics % −15.6 5.8 6.727.1 Di aromatics % 88.1 91.7 89.6 93.2 Tri aromatics % 90.8 94.6 94.496.8 Tri⁺ aromatics % 91.4 94.7 94.1 96.2‘silica’ indicates use of the catalyst of Example 6‘titania’ indicates use of the catalyst of Example 5

Table 4 clearly illustrates the benefit of using titania as a refractoryoxide in the catalyst composition. The largest benefit is seen in thehydrogenation of monoaromatic compounds. At 1.5 l.l⁻¹.h⁻¹ spacevelocity, the catalyst prepared with titania can achieve positivearomatics conversion, meaning a conversion beyond eliminating themono-aromatic compounds that are produced by the hydrogenation of thedi-aromatics, thus also converting those that were originally present inthe feed.

At an hourly liquid space velocity of 1.0 l.l⁻¹.h⁻¹, thesilica-containing catalysts can match this conversion level. However,the titania counterpart increased the conversion of these mono-aromaticcompounds to 27.1%, maintaining the gap of ˜20% difference in theconversion of these most difficult-to-eliminate compounds in the feed.This indicates a superior hydrogenation activity previously seen onlywith noble metal catalysts.

When translated into relative volumetric activity, the hydrogenationactivity for mono-aromatic compounds can be seen to be at least 60-70%higher for the titania catalysts, based on the similar activitiesachieved at 1.0 l.l⁻¹.h⁻¹ with the silica sample, as achieved at 1.5l.l⁻¹.h⁻¹ with the titania sample.

In the hydrogenation of heavier aromatic compounds, such asdi-aromatics, tri-aromatics and heavier, the titania-containing samplepreserves its leading performance as compared to the silica counterpart.

Example 9 Comparison of Activity Using Titania of Different Origin

Following the preparation route described in Example 5, several sampleshave been prepared using titania of various origin but combined with thesame amount of nickel and molybdenum. Available properties, such asB.E.T. surface area, pore volume obtained from the adsorption curve ofthe B.E.T. method, and average particle size of the titania powders areshown in Table 5. The percentage of anatase content is also shown.

TABLE 5 Origin, type, B.E.T. surface area (SA), pore volume (PV), andparticle size (D_(v50)) of the powder, the anatase content, and theoffset of temperature required (Treq) for 10 ppmw sulfur in product whenprocessing full range straight run (‘virgin’) gas oil under trickle flowconditions. N₂ SA N₂ PV D_(v50) anatase ΔTreq Origin Type (m²/g) (cm³/g)(μm) (%) (° C.) Degussa P25 50 0.14 3.36 80 −12 Millenium G5 293 0.34*22 100 −1 DT-51D 88 0.32 1.56 100 −17 Haishunde TiO₂** 354 0.37 5.11 100−17 *obtained from another LOT of G5 with identical grade **FCT010925

The obtained extrudates were crushed and sieved into 30-80 mesh fractionthat is suited for catalytic testing in a tubular trickle flow reactor.After proper sulfidation using common refinery practice forhydrotreating catalysts, the activity in hydrodesulfurization wasmeasured. A full range straight run (‘virgin’) gas oil was used as feedhaving a 1.63 wt % sulfur content. The test was performed at 1.75l.l⁻¹.h⁻¹ liquid hourly space velocity with 55 bar hydrogen partialpressure. The activity is expressed as the difference in the requiredtemperature to process the above mentioned feed to 10 ppmw sulfur inproduct, using the performance of a catalyst prepared by followingExample 5 as a base case (i.e. providing the reference temperature ofactivity). These values are also presented in Table 5. Note that alarger absolute value of the negative numbers (a larger difference)translates into a more active catalyst compared to the reference.

From Table 5 it is clear that with titania powders having considerablydifferent physical properties, it is still possible to achieve asignificant increase in performance. Up to 17° C. improvement inactivity can be associated to using various titania sources.

Based on the average particle size of the titania powders employed, thehighest activity can be associated with particle sizes below 10 μm inthe initial titania used.

Example 10 Comparison of Activity with Increasing Titania Content

Following the preparation route described in Example 5, three additionalsamples were prepared using refractory oxides with increasingproportions of titania. The catalytic performance was tested underidentical conditions as described in Example 9. The obtained performanceis expressed in terms of pseudo first order reaction rate constants inthe HDS reaction in (Table 6). Note that a higher reaction rate constantindicates a more active catalyst.

TABLE 6 Refractory oxide, the percentage of titania in the refractoryoxide and the relative temperature required to reach 10 ppmw sulfur inproduct Titania content as Pseudo first order a percentage of thereaction rate Refractory refractory oxide constant k(HDS) oxide (wt %)(l · l⁻¹ · h⁻¹ · % wt S⁻¹) Silica¹ 0 19.9 Silica-titania² 70 27.1Titania³ 100 37.2 ¹silica used is SIPERNAT 50 ²silica-titania used isFTS 01 from Haishunde ³titania used is FCT010925 from Haishunde

Table 6 clearly demonstrates that with increasing titania content in therefractory oxide, the performance of the catalysts is improved: higherpseudo reaction rate constant were obtained for the removal of sulfur.

Example 11 NiO/MoO₃/WO₃/SiO₂ 30.2 wt %/19.1 wt %/30.8 wt %/19.9 wt %

In a 5 litre autoclave 3088 g water were weighed and heated to 80° C.Upon reaching the temperature, 90.9 g silica (SIPERNAT 50), 240.8 gnickel carbonate (39 wt % Ni), 94.1 g ammonium heptamolybdate (81.63 wt% MoO₃), and 143.6 g ammonium metatungstate (86.11% WO₃) were added. Allof the metal-containing components were added in powder form. Followingthe addition of 122.7 g ammonia solution (25 wt % ammonia content), thetemperature was kept at 80° C. for 30 minutes, while the pH of theresulting slurry was 8.8 (measured at room temperature for a small testportion).

After 30 minutes the heating was switched off and the slurry was spraydried. In total, 407.7 g of solid material were collected. This powderwas extruded directly, after which it was dried and calcined at 300° C.

Example 12 NiO/MoO₃/WO₃/TiO₂ 30.2 wt %/19.1 wt %/30.8 wt %/19.9 wt %

In a 5 litre bulb, 3094 g water were heated to 80° C. Subsequently 84.2g titania, 240.8 g nickel carbonate (39 wt % Ni), 94.1 g ammoniumdimolybdate (81.63 wt % MoO₃), 143.6 g ammonium metatunsgstate (86.11%WO₃)—all added in powder form—and 122.7 g ammonia solution (25 wt %ammonia) were added, while maintaining the temperature at 80° C. The pHof the slurry was 8.8.

After 30 minutes the heating was switched off, and the spray drying ofthe slurry began. The resulting powder was extruded, dried and calcinedat 300° C.

Example 13 Comparison of HDS Activity of the Catalysts of Example 11 andExample 12

Gas oil HDS testing was performed in a nanoflow setup under trickle flowconditions, using full range (“virgin”) straight run gas oil as feed.The catalysts was crushed and sieved into a 30-80 mesh size fraction.After drying, they were loaded into the reactors with SiC as diluent toensure proper plug flow conditions. Prior to testing, the catalysts weresulfided with the feed itself, according to a standard refineryprocedure.

Testing was performed at 345° C., under 55 bar hydrogen partialpressure, with hydrogen gas rate of 300 Nl/kg feed. No additional H₂Swas added to the recycle gas, while the liquid hourly space velocity(LHSV) was varied between 1.75 and 2.5 l.l⁻¹.h⁻¹ values.

The obtained product sulfur contents corrected to the target conditions,the pseudo first order reaction rate constants, and the calculatedrelative volumetric activity based on the performance of Example 11 isshown in Table 7.

TABLE 7 Actual sulfur in product, temperature required for 10 ppmwsulfur in product, and relative volumetric activities of catalyststested in full range straight run (“virgin”) gas oilhydrodesulfurization Example 11 Example 12 Silica titania Target LHSV (l· l⁻¹ · h⁻¹) 1.75 2.5 1.75 2.5 Sulfur in product (ppmw) 24 341 9 118Temperature required for 359 408 344 387 10 ppmw sulfur in product (°C.) Relative Volumetric Activity (%) 100 100 166 182

As it can be seen from Table 7, the catalyst of Example 12 achievedlower than 10 ppmw sulfur in product under the chosen test condition at1.75 l.l⁻¹.h⁻¹ space velocity. This was not possible with thesilica-containing counterpart (Example 11). Furthermore, the requiredtemperatures for 10 ppmw sulfur in product are systematically lower forthe titania sample with an activity gap of approximately 15° C. at bothspace velocities. This clearly demonstrates the benefit of using titaniawith the applied composition and preparation route.

Example 14 NiO/MoO₃/WO₃/Al₂O₃ 29.9 wt %/19.2 wt %/30.9 wt %/20.0 wt %

In this preparation, Example 7 from WO 00/41810 was reproduced with theaddition of 20 wt % alumina as refractory oxide after the precipitationwas complete.

Solution A: 52.95 g ammonium heptamolybdate (81.62 wt % MoO₃) wasdissolved in 2400 ml water in a 5 litre bulb. In addition, 80.8 gammonium metatungstate (86.11 wt % WO₃) were added and dissolved in theaqueous mixture. The mixture was then heated to 90° C.

Solution B: 135.5 g nickel carbonate (39 wt % Ni) were part-dissolved in600 ml water and heated to 90° C.

Solution B was pumped into solution A over a 10 minute period of timewith vigorous stirring. The resulting solution was kept at 90° C. withstirring for 20 hours. After this reaction period, 71.5 grams of VersalAlumina were added to the slurry. 30 minutes after the addition of thealumina, the heating was switched off and the slurry was spray-dried.200.3 g solid material were collected in total. The powder was turnedinto the final shaped product by extrusion, drying, and calcination at300° C.

Example 15 NiO/MoO₃/WO₃/TiO₃ 29.9 wt %/19.2 wt %/30.9 wt %/20.0 wt %

Example 14 Repeated with Use of Titania Instead of Alumina

In this preparation, Example 7 from WO 00/41810 was reproduced as inExample 14 with the modification of replacing the refractory oxide by 20wt % titania.

Solution A: in a 5 litre bulb 52.95 g ammonium heptamolybdate (81.62 wt% MoO₃) was dissolved in 2400 ml water and then 80.8 g ammoniummetatungstate (86.11 wt % WO₃) was added and dissolved. The mixture washeated to 90° C.

Solution B: 135.5 g nickel carbonate (39 wt % Ni) was slurried in 600 mlwater and heated to 90° C.

Solution B was pumped in solution A over a 10 minute period of time withvigorous stirring. The resulting solution was kept at 90° C. whilestirring for 20 hrs. After this reaction period, 47.3 grams of titaniawas added to the slurry and mixed thoroughly. 30 minutes later theheating was switched off, and the slurry was spray dried. In total,189.0 g of solids were recovered. The powder was turned into the finalshaped product by compaction, drying and calcination at 300° C.

Example 16 Comparison HDS Performance of the Catalysts of Example 14 andExample 15

Gas oil HDS testing was performed in a nanoflow setup under trickle flowconditions, using full range (“virgin”) straight run gas oil as feed.The catalysts were crushed and sieved into a 30-80 mesh size fraction.After drying, they were loaded into the reactors with SiC as diluent toensure proper plug flow conditions. Prior to testing, the catalysts weresulfided with the feed itself, according to a standard refineryprocedure.

Testing was performed at 55 bar hydrogen partial pressure. An additionaltesting condition at 40 bar hydrogen pressure was also measured. Theliquid hourly space velocity (LHSV) was set to 1.75 for both 55 bar and40 bar conditions. The feed contained 1.6 wt % sulfur.

Test data with sulfur in product, the temperature required to processthe feed to 10 ppmw sulfur, the pseudo first order reaction rateconstants, and the relative volumetric activity based on the reactionrate constants are given in Table 8.

TABLE 8 Sulfur in product, temperature required for 10 ppmw productsulfur content, pseudo first order reaction rate constants and relativevolumetric activities of catalysts in processing full range straight run(‘virgin’) gas oil Example 14 Example 15 Alumina titania Hydrogenpartial pressure (bar) 55 40 55 40 Sulfur in product (ppmw) 37 48 5 13Temperature required for 340 354 310 334 10 ppmw sulfur in product (°C.) k_(HDS) (l · l⁻¹ · h⁻¹ · % wt S⁻¹) 55.1 47.6 158.0 93.5 RelativeVolumetric Activity (%) 100 100 287 197

It is clear from Table 8 that the use of titania in the catalystcomposition has significantly improved the activity. The sulfurremaining in the product was lower at both pressures applied forhydrotreating. The temperatures required to process the feed to 10 ppmwsulfur product content is 30° C. lower at 55 bar hydrogen pressure forthe titania-containing catalyst, and this advantage is only diminishedto a 20° C. at 40 bar. When translated into relative volumetricactivities, the titania counterpart is approximately twice as active asthe alumina version at 40 bar (4 Mpa), and close to three times asactive at 55 bar (5.5 Mpa) hydrogen partial pressures.

1. A process for the preparation of a catalyst composition, wherein saidprocess comprises: combining a Group VIb metal compound, a Group VIIImetal compound, and a titania-containing refractory oxide material,wherein said titania-containing refractory oxide material comprises 50wt % or more titania, on an oxide basis, and includes titania powderhaving an average particle diameter of 50 microns or less and a B.E.T.surface area in the range of from 10 to 700 m²/g, in the presence of aprotic liquid and an alkali compound; forming a coprecipitate; andrecovering said coprecipitate which comprises a Group VIb metalcomponent, a Group VIII metal component, and a refractory oxidematerial.
 2. A process as claimed in claim 1, wherein at least one ofthe metal compounds used in the combining step is partly in solid stateand partly in dissolved state.
 3. A process as claimed in claim 2, whichcomprises heating a precursor composition which is in the form of, or isrecovered from, a slurry, after aging at a temperature in the range offrom 20 to 95 deg C for a minimum of 10 minutes, said slurry beingobtained by coprecipitating, at a sufficient time and temperature, saidGroup VIb compound, said Group VIII compound, said titania-containingrefractory oxide material, and said alkali compound, in a protic liquid.4. A process as claimed in claim 3, wherein the titania used has aparticle diameter of 10 microns or less.
 5. A process as claimed inclaim 4, wherein the coprecipitate is recovered by spray-drying.
 6. Aprocess as claimed in claim 5, wherein said alkali compound is ammoniaor a component that will generate ammonium ions in the protic liquidused.
 7. A process as claimed in claim 6, wherein said coprecipitate isfurther subjected to any one or more of the following process stepscarried out in any appropriate order: cooling; optionally isolating;drying; shaping, preferably by extrusion using no extrusion aids;calcining; sulphiding.
 8. A process as claimed in claim 1, wherein allmetal compounds are added to the protic liquid as solids.
 9. A catalystcomposition as prepared by the process of claim 1, 2, 3, 4, 8, 5, 6, or7, wherein said catalyst composition comprises: a Group VIb metalcomponent present in the amount in the range of from 5 to 90 wt. %, asthe oxide and based on the total coprecipitate; a Group VIII metalcomponent present in the amount in the range of from 2 to 80 wt. %, asthe oxide and based on the total coprecipitate; and a titania-containingrefractory oxide material having present therein 50 wt. % or moretitania, on an oxide basis, and includes titania powder having anaverage particle diameter of 50 microns or less and a B.E.T. surfacearea in the range of from 10 to 700 m²/g.
 10. A method of preparing acatalyst composition, said method comprises: combining a Group VIb metalcompound, a Group VIII metal compound and a titania-containingrefractory oxide material, which comprises titania powder having anaverage particle diameter of 20 microns or less, in the presence of aprotic liquid; subjecting a mixture resulting from said combining stepto coprecipitation conditions thereby forming a coprecipitate solid; andrecovering said coprecipitate solid comprising at least 50 wt % titania,on an oxide basis.
 11. A method as recited in claim 10, wherein at leastone of the metal compounds combined in the presence of said proticliquid is partly in solid state and partly in dissolved state.
 12. Amethod as recited in claim 11, wherein said recovering step includes:heating said coprecipitate solid at an elevated temperature so as toyield said composition.
 13. A method as recited in claim 12, whereinsaid protic liquid comprises water, and further combined with saidnon-noble Group VIb metal compound, said non-noble Group VIII metalcompound, and said titania-containing refractory oxide is an alkalicompound.
 14. A method as recited in claim 13, wherein saidcoprecipitation conditions include maintaining said mixture at acoprecipitation temperature in the range of from 25 to 95° C. for aperiod of time in the range of from 10 minutes to 2 hours.
 15. A methodas recited in claim 14, wherein said elevated temperature is in therange of from 100° C. to 600° C.
 16. A method as recited in claim 15,wherein said alkali compound is ammonia or a material that will generateammonium ions in the protic liquid of said mixture.
 17. A method asrecited in claim 16, wherein said titania powder used in said combiningstep has an average particle diameter of 10 microns or less.
 18. Amethod as recited in claim 17, wherein said catalyst composition isrecovered by spray drying.